February 23, 2018:

Time-Lock Puzzles in Relation to Bitcoin

Grady Yu

Time-lock puzzles enable a published message to be decoded only after
a set time period has elapsed. The original construction by
Rivest,
Shamir, and Wagner (1996) relies upon "inherently sequential computation" and
standard RSA hardness. An alternative approach shown by
Jager (2015)
treats the Bitcoin network as a "computational reference clock" to avoid
the expensive decoding step.